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나트륨 Na, Sodium

- 나트륨 재흡수

나트륨은 전신에 분포하고 주로 세포 외액에 존재하며 세포외액의 침투압유지와 세포외액량을 유지하는 역할을 하며 체중의 약 00.15~0.2%를 차지하고 있다. 칼륨과 같이 세포의 물질교환의 역할을 한다.

 

1. 나트륨의 기능

나트륨은 체내의 수분 평형 조절에 관여하며 산과 알칼리의 균형 유지에 필수적인 요소다. sodium pump 작용에 의해 능동적으로 수송됨으로써 정상적인 근육의 자극반응을 조절하며 신경을 자극시켜 정상적인 근육의 흥분성과 과민성을 유지하는데 관여. 근육의 수축과 혈액의 양과 혈압을 유지하는데 필요합니다. 신장은 이들 전해질의 주요 조절 기관이다.

Maintaining body fluid volume in animalsMain articles: Renin-angiotensin system and atrial natriuretic peptide
The serum sodium and urine sodium play important roles in medicine, both in the maintenance of sodium and total body fluid homeostasis, and in the diagnosis of disorders causing homeostatic disruption of salt/sodium and water balance.

In mammals, decreases in blood pressure and decreases in sodium concentration sensed within the kidney result in the production of renin, a hormone which acts in a number of ways, one of them being to act indirectly to cause the generation of aldosterone, a hormone which decreases the excretion of sodium in the urine. As the body of the mammal retains more sodium, other osmoregulation systems which sense osmotic pressure in part from the concentration of sodium and water in the blood, act to generate antidiuretic hormone. This, in turn, causes the body to retain water, thus helping to restore the body's total amount of fluid.

There is also a counterbalancing system, which senses volume. As fluid is retained, receptors in the heart and vessels which sense distension and pressure, cause production of atrial natriuretic peptide, which is named in part for the Latin word for sodium. This hormone acts in various ways to cause the body to lose sodium in the urine. This causes the body's osmotic balance to drop (as low concentration of sodium is sensed directly), which in turn causes the osmoregulation system to excrete the "excess" water. The net effect is to return the body's total fluid levels back toward normal.

[edit] Maintaining electric potential in animal tissuesMain article: Action potential
Sodium cations are important in neuron (brain and nerve) function, and in influencing osmotic balance between cells and the interstitial fluid, with their distribution mediated in all animals (but not in all plants) by the so-called Na+/K+-ATPase pump.[23] Sodium is the chief cation in fluid residing outside cells in the mammalian body (the so-called extracellular compartment), with relatively little sodium residing inside cells. The volume of extracellular fluid is typically 15 liters in a 70 kg human, and the 50 grams of sodium it contains is about 90% of the body's total sodium content.

[edit] Role of sodium in plant biologyAlthough sodium is not considered an essential micronutrient in most plants, it is necessary in the metabolism of some C4 plants, e.g. Rhodes grass, amaranth, Joseph's coat, and pearl millet.[24] Within these C4 plants, sodium is used in the regeneration of phosphoenolpyruvate (PEP) and the synthesis of chlorophyll. In addition, the presence of sodium can offset potassium requirements in many plants by substituting in several roles, such as: maintaining turgor pressure, serving as an accompanying cation in long distance transport, and aiding in stomatal opening and closing.[25]

Due to increasing soil salinity, osmotic stress and sodium toxicity in plants, especially in agricultural crops, have become worldwide phenomena. High levels of sodium in the soil solution limit the plants' ability to uptake water due to decreased soil water potential and, therefore, may result in wilting of the plant. In addition, excess sodium within the cytoplasm of plant cells can lead to enzyme inhibition, which may result in symptoms such as necrosis, chlorosis, and possible plant death.[26] To avoid such symptoms, plants have developed methods to combat high sodium levels, such as: mechanisms limiting sodium uptake by roots, compartmentalization of sodium in cell vacuoles, and control of sodium in long distance transport.[27] Many plants store excess sodium in old plant tissue, limiting damage to new growth


2. 나트륨의 결핍

나트륨 결핍은 신장병, 만성설사, 과도한 구토, 심한 발한, 부신장애와 갑상선 저하증, 단백질 결핍으로 오기 쉽다. 나트륨 결핍이 되면 식욕부진, 소화불량, 장내가스, 근육위축, 체중감소, 구토, 탈수, 두통, 혼동, 발작, 혼수, 저혈압, 알레르기 증상, 기관지 약화, 간기능 저하, 성장장애, 모유분비감소, 환각, 심계항진 등이 발생할 수 있다.

3. 나트륨의 과잉

나트륨 과다는 카드뮴, 철, 셀레늄, 니켈, 칼슘, 마그네슘, 칼륨 등의 과다에 의해서 나타날 수 있다.  나트륨이 과도하면 갈증, 피로, 민감성, 잠이 많고, 신경불안정, 정서불안, 스트레스에 민감한 반응, 발작, 자살 충동, 죽음을 유발할 수 있다. 또한 체액을 저류시켜 혈압을 상승시킴, 위암 발병률을 상승시킨다.

나트륨 폭발성 금속 : http://youtu.be/8PEVmflpUCo